Acoustic microphone arrays

ABSTRACT

Acoustic microphone array systems including arrays of microphones placed on a printed circuit board or other substrate in asymmetric patterns. A plurality of additional non-microphone components also reside on the board. The asymmetric placement of the microphones in the array provides flexibility in physically accommodating the additional non-microphone components.

BACKGROUND

The present disclosure relates generally to acoustic microphone systemsincorporating an array of microphone elements.

SUMMARY

According to aspects of the disclosure, an acoustic microphone arraysystem includes a substrate and an array of acoustic microphones. Thearray have a first group of acoustic microphones placed on the substratein an asymmetric pattern and a second group of microphones. The radialdistance of each microphone in the first group of microphones may belarger than the radial distance of each microphone in the second groupof microphones. The substrate can be circular, or have a variety ofother shapes, depending on the embodiment.

The second group of microphones can be placed on the substrate in anasymmetric pattern in some embodiments. In some implementations, theradial distance of an innermost microphone in the second group ofmicrophones is no more than about 25% of a radial distance of anoutermost microphone in the first group of microphones.

In some embodiments, the system further includes one or more packagedintegrated circuits placed on the substrate at a radial distance greaterthan the radial distance of the innermost microphone in the second groupand less than the radial distance of the outermost microphone in thefirst group. In further embodiments, the radial distance of an innermostmicrophone in the first group of microphones is no more than 50% of theradial distance of an outermost microphone in the first group ofmicrophones. The packaged integrated circuits can be placed on thesubstrate at a radial distance between the radial distance of theinnermost microphone in the first group of microphones and the radialdistance of the outermost microphone in the first group of microphones.

The first group of microphones in some embodiments includes Nmicrophones, and the maximum difference in polar angle between any twoangularly adjacent microphones of the first group of microphones is atleast 130% of 360/N. The system can further include a packagedintegrated circuit placed between angularly adjacent microphones in thefirst group of microphones.

In some embodiments, the system includes a group of packaged integratedcircuits mounted on the substrate together with the first and secondgroups of microphones. The group of packaged integrated circuits caninclude one or more networking devices and one or more microprocessors.

The system can further include a processor placed on the substrate andconfigured to perform one or both of acoustic echo cancelation andbeamforming on signals output by the first and second groups ofmicrophones.

The system can further include a processor configured to combine signalsoutput by the first group of acoustic microphones to generate outputsound within a first frequency range and to combine signals output bythe second group of acoustic microphones to generate output sound withina second frequency range. The first and second frequency can, in someembodiments, cover a combined frequency that at least includesfrequencies from 1,000 Hz to 14,000 Hz. A maximum frequency in the firstfrequency range can be substantially less than 14,000 Hz, and a minimumfrequency of the second frequency range can be substantially more than1,000 Hz.

According to some embodiments, the processor is remote from the firstand second groups of microphones, and in communication with the firstand second groups of microphones via a network.

According to further aspects of the disclosure, an audio system isprovided that includes a substrate, an array of acoustic microphones,and a processor. The array can include a first group of acousticmicrophones arranged on the substrate in an asymmetric pattern> Thearray may further include a second group of acoustic microphonesarranged on the substrate in an asymmetric pattern. The radial distanceof an innermost microphone of the first group of microphones from acenter of the substrate may be greater than a radial distance of anoutermost microphone of the second group of microphones and no more thanabout 40% of the radial distance of an outermost microphone of the firstgroup of microphones. The radial distance of the outermost microphone inthe second group of microphones may be no more than about 25% of theradial distance of the outermost microphone in the first group ofmicrophones. The processor can be configured to combine signals outputby the first group of acoustic microphones to generate output soundwithin a first frequency range and to combine signals output by thesecond group of acoustic microphones to generate output sound within asecond frequency range. In some embodiments, the processor is remotefrom the first and second groups of microphones, and in communicationwith the first and second groups of microphones via a network.

According to yet further aspects of the disclosure, a method ofgenerating a microphone layout for an array microphone is provided. Themethod can include placing each microphone in first and second groups ofmicrophones in an arbitrary initial position on the substrate.Subsequent to said placing each microphone, the microphones can bearranged at an initial set of microphone positions.

The method can include, with a software simulator, determining arrayperformance with the microphones at the initial set of microphonepositions.

The method can also include, subsequent to said determining arrayperformance, adjusting placement of one or more microphones in one orboth of the first group of microphones and the second group ofmicrophones such that the microphones are arranged at an adjusted set ofmicrophone positions.

The method can additionally include, with the software simulator,determining adjusted array performance at the adjusted set of microphonepositions. The method can further include repeating said adjustingplacement and determining adjusted array performance said adjusted arrayperformance indicates sufficient performance at a set of finalmicrophone positions in which the first group of microphones is arrangedin a first asymmetric pattern and the second group of microphones isarranged in a second asymmetric pattern.

The method can also include placing a plurality of non-microphonecomponents on a substrate.

At the set of final microphone positions, each microphone in the firstgroup may be located at a longer radial distance from the center of thesubstrate than each microphone in the second group.

The placing of the plurality of non-microphone components may beperformed prior to said placing each microphone in the first and secondgroups of microphones in an initial position on the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an audio/video system incorporating one or moremicrophone systems according to certain embodiments.

FIG. 2 is a block diagram showing a microphone system including anasymmetric array of microphones according to certain embodiments.

FIGS. 3A-3B illustrate top and bottom views of a top board of atwo-board microphone system including an asymmetric array ofmicrophones, according to certain embodiments.

FIGS. 3C-3D illustrate top and bottom views of a bottom board configuredto mate with the top board of FIGS. 3A-3B.

FIG. 4 illustrates directional performance of the microphone system ofFIGS. 3A-3D at 0, 90, 180, and 270 degrees.

FIG. 5 illustrates a single-board microphone system including anasymmetric array of microphones according to additional embodiments.

FIG. 6 illustrates a method of placing microphones in a microphone arrayaccording to certain embodiments.

DETAILED DESCRIPTION

For purposes of summarizing the disclosure, certain aspects, advantagesand novel features of the disclosures have been described herein. It isto be understood that not necessarily all such advantages can beachieved in accordance with any particular embodiment of the disclosuresdisclosed herein. Thus, the disclosures disclosed herein can be embodiedor carried out in a manner that achieves or optimizes one advantage orgroup of advantages as taught herein without necessarily achieving otheradvantages as can be taught or suggested herein.

System Overview

Audio processing systems include sophisticated computer-controlledequipment that receive and distribute sound in a space. Such equipmentcan be used in business establishments, bars, restaurants, conferencerooms, concert halls, churches, or any other environment where it isdesired to receive audio inputs from a source and deliver it to one ormore speakers for people to hear. Some modern systems incorporateintegrated audio, video, and control (AV&C) capability to provide anintegrated system architecture. An example of such a system is the QSC®Q-SYS™ Ecosystem provided by QSC, LLC, which provides a scalablesoftware-based platform. A simplified representation of an audio/videosystem 100 is shown and described with respect to FIG. 1 .

The system 100 includes a processing core 120 that includes one or moreprocessors 122, a network 130, one or more microphone systems 140,loudspeakers 150, cameras 160, control devices 170, and third partydevices 180. The processor(s) 122 of the illustrated embodiment is ageneral purpose microprocessor, although alternative configurations caninclude an audio processor designed for audio digital signal processing.

The microphone systems 140 can include one or more array microphonesystems, which can be any of the array microphone systems describedherein including microphones mounted in an asymmetric array, althoughother types of microphone systems can also be included. The cameras 160can include one or more digital video cameras. The control devices 170can include any appropriate user input devices such as a touch screen,computer terminal or the like. While not shown in FIG. 1 , the system100 can also include appropriate supporting componentry, such as one ormore audio amplifiers or equalization components.

The third party devices 180 can include one or more laptops, desktops orother computers, smartphones or other mobile devices, projectors,screens, lights, curtains/shades, fans, and third party applicationsthat can execute on such devices, including third party conferencingapplications such as Zoom or Microsoft® Teams or digital voiceassistants like Apple's Siri®.

While illustrated as separate components in FIG. 1 , depending on theimplementation, microphone systems 140, loudspeakers 150, cameras 160,control devices 170, and/or third party devices 180 can be integratedtogether. For example, some or all of a microphone array, loudspeaker,camera, and touch screen can be integrated into a common packaging.

In operation, the microphone(s) 140 detect sounds in the environment,convert the sounds to digital audio signals, and stream the audiosignals to the processing core 120 over the network 130. Theprocessor(s) 122 receives the audio signals and performs digital signalprocessing on the signals. For example, the processor 122 can performfixed or adaptive echo cancellation, fixed or adaptive beamforming toenhance signals from one or more directions while suppressing noise andinterference from other directions, amplification, or any combinationthereof. Other types of noise processing, spatial filtering, or otheraudio processing can be performed depending on the embodiment. In someembodiments, instead of the microphone 140 sending raw digital audiosignals to the processing core 120, one or more processors on themicrophone system 140 itself perform some or all of the echocancellation, beamforming, amplification, or other processing prior tosending the signal to the processing core 120.

As mentioned, the microphone system 140 can include one or moremicrophone arrays including a plurality of individual microphoneelements. As these microphone arrays become more feature-rich, theyinclude increasing numbers of not only microphone elements but othercomponents (processors, sensors, electrical components, etc.), as willbe described in more detail including with respect to FIGS. 3A-3D andFIGS. 5 and 6 . However, existing microphone arrays such as those usedfor beamforming typically employ microphones arranged in rigidly definedgeometries. These can include concentric rings, straight lines, squares,rectangles, or the like. As the number and sophistication of microphonecomponents continues to increase, it can be difficult to physicallyaccommodate rigidly defined microphone geometries together with theother components. Certain embodiments described herein address these andother challenges by allowing flexible microphone arrangements, freeingup real estate on the microphone board.

Microphone System

FIG. 2 shows a block diagram of an example of a microphone system 140that can be used with the system 100 of FIG. 1 or with any of thesystems described herein. The microphone system 140 includes a housing200, a plurality of microphones 202 arranged in an asymmetric array, oneor more discrete electrical components 204, one or more integratedcircuits 206, one or more outputs 208, one or more sensors 210, one ormore user interface components 212, and one or more mounting or otherhardware components 214.

Some or all of the aforementioned components 202-214 can be mounted onone or more substrates or boards 216, which can be printed circuitboards (PCBs) for example. The boards 216 can be contained, enclosed, orotherwise supported by the housing 200, which can be a single-pieceenclosure (e.g., a single-piece molded plastic), or a combination ofpieces, such as a combination of molded plastic and perforated acousticmesh to facilitate ingress and egress of incoming and outgoing sound.Depending on the embodiment, the microphone system 140 can be configuredfor placement or installation on or in a table-top, on or within aceiling (e.g., to replace a ceiling panel), on or in a wall, or in someother desired location.

Examples of Asymmetric Microphone Systems

FIGS. 3A-3D depict views of a top board 216 a (FIGS. 3A-3B) and a bottomboard 216 b (FIGS. 3C-3D) of one example of microphone system 140, wherein an assembled configuration the top board 216 a is stacked on thebottom board 216 b, with the bottom of the top board 216 a (FIG. 3B)facing the top of the bottom board 216 b (FIG. 3C), and the stack isplaced in a housing 200 (not shown in FIGS. 3A-3D). In the illustratedembodiment top board 216 a and the bottom board 316 b are printedcircuit boards (PCB) each having a diameter D of 11 cm, although othersizes are possible.

FIGS. 3A-3B respectively show top and bottom views of the top board 216a. Referring to FIG. 3B, a plurality of microphones 202 a-202 p aremounted to the bottom of the top board 216 a. Referring to FIG. 3A, thetop board 216 a includes a plurality of circular holes 302 eachcorresponding to, and exposing a portion of the underside of, acorresponding one of the microphones 202 a-202 p. The holes 302 canfacilitate detection of sound waves by the microphones 204 a-204 pincident on the microphone system 140 from the top of the top board 216a through the housing 200.

The microphones 202 a-202 p of the embodiment illustrated in FIGS. 3A-3Dare each omnidirectional piezo electric MEMS-based acoustic microphonetransducers capable of detecting sound in a frequency range of 10 Hz to20,000 Hz and a high linearity frequency range of 80 Hz to 8,000 Hz, andare housed in integrated circuit packages mounted on the top board 216a. In other embodiments, other types of microphones can be used such asdynamic or condenser microphones.

The microphones 202 a-202 p of the illustrated embodiment include afirst group of nine microphones 202 a-202 i and a second group of sevenmicrophones 202 j-202 p. The processor 122 can process and/or combinesignals output from the first group of microphones 202 a-202 i togenerate sound content within a first frequency range, and processand/or combine signals output from the second group of microphones 202j-202 p to generate output sound content within a second frequencyrange.

For example, the processor 122 may filter signals output by the firstgroup of microphones 202 a-202 i using one or more first filters (e.g.,bandpass filters), and combine the filtered outputs to generateprocessed audio within the first frequency range, and filter signalsoutput by the second group of microphones 202 j-202 p using one or moresecond filters (e.g., bandpass filters), and combine the filteredoutputs to generate processed audio within the second frequency range.

The second frequency range according to some embodiments is higher thanthe first frequency range, although the frequency ranges can overlapsomewhat. In some embodiments, the maximum frequency of the firstfrequency range and the minimum value of the second frequency range arevalues at which the first group and the second group have similar noiseperformance. A variety of possible values are possible for the first andsecond frequency ranges. Here just a few examples:

First Frequency Range (Hz) Second Frequency Range (Hz) 20-1,2001,200-20,000 80-1,200 1,200-20,000 20-2,000 2,000-20,000 80-2,0002,000-20,000 20-3,000 3,000-20,000 80-3,000 3,000-20,000  80-,1,2001,200-8,000  80-2,000 2,000-8,000  80-3,000 3,000-8,000 

While the examples provided indicate that the first and second frequencyranges overlap exactly at a single value (1,200, 2,000, or 3,000 Hz), insome embodiments the ranges can have larger overlaps, such as by 5, 10,100, 1,000, 2,000, 3,000, 5,000 or more Hz, or by values between theseamounts. Depending on the embodiment, the combined first and secondfrequency ranges can at least cover certain voice frequency bands, suchas 300-3,400 Hz, 50-7,000 Hz, 50-14,000 Hz, or 20-20,000 Hz. Thefrequency range can be relatively broad to capture not only speechbandwidths, but other sounds for improved noise handling or otherpurposes.

As shown in FIGS. 3A-3B, the microphones 202 a-202 o of the illustratedembodiment (excluding the central microphone 202 p, which may not beincluded in some embodiments) are placed such that each microphone 202a-202 o is at a unique radial distance R and different polar angle Pfrom a center of the substrate as compared to the other microphones inthe array. In the illustrated embodiment, the top board 216 a has adiameter of 11 cm, and the microphones are positioned at the followingunique radial distances R and polar angles P from the center of thesubstrate:

Microphone R(cm) P(degrees) 202a 4.68 243.07 202b 4.35 292.30 202c 3.36309.68 202d 4.14 8.46 202e 3.89 44.01 202f 4.48 87.59 202g 2.42 143.30202h 4.92 179.85 202i 2.92 199.18 202j 0.79 218.24 202k 0.83 283.17 202l1.06 322.61 202m 0.73 25.63 202n 0.96 89.29 202o 0.87 158.60 202p 0.000.00

The radial distance R and polar angle are measured from the center ofthe board 216 a to the center of the hole 302 (FIG. 3A) of thecorresponding microphone 202, which also corresponds to the center ofthe package of each microphone 202 (FIG. 3B). In other implementations,rather than each microphone having a unique polar angle from all othermicrophones in the array, each microphone in a particular group has aunique polar angle as compared to the other microphones in that group,but may share a polar angle with one or more microphones in anothergroup. In yet further implementations, one or more microphones in agroup may share a common radial distance with other microphones in thatgroup.

The sparse, scattered arrangement of the microphones 202 a-202 i in thefirst group can be helpful in accommodating additional componentry,particularly larger integrated circuits or other relatively largecomponents. Variability in radial distances of microphones can helpachieve this benefit.

For instance, in the illustrated embodiment, the radial distance of theinnermost microphone 202 g in the first group is about 49% (2.42/4.92)of the radial distance of the outermost microphone 202 h in the firstgroup, and about 44% (2.42/5.5) of the radius of the top board 216 a. Invarious implementations, the radial distance of the innermost microphone202 g in the first group is no more than about 30, 35, 40, 45, 49, 50,55, 60, or 70% of the radial distance of the outermost microphone 202 hin the first group, and/or of the radius of the board 216.

Variability in polar angle of microphones in a group can also helpachieve a sparse, scattered geometry to facilitate design flexibility.In a rigidly circular array, each microphone 202 in a group of ninemicrophones would be 40 degrees apart (360/9). In the illustratedembodiment, on the other hand, the maximum difference in polar anglebetween any two angularly adjacent microphones in the first group isbetween microphone 202 f and microphone 202 g, which are 55.71 degreesapart (about 139% [55.71/40] of the angular separation in a circularsymmetric ring having the same number of microphones). In variousimplementations, the maximum difference in polar angle between any twoangularly adjacent microphones in a group (e.g., an outer group, innergroup, and/or a group of microphones for a particular frequency range)of N microphones is at least about 120, 130, 135, 140, 145, 150, 160, or170% of 360/N.

The minimum difference in polar angle between any two angularly adjacentin the first group is between microphone 202 b and microphone 202 c,which are 17 degrees apart (about 43% [17/40] of the angular separationin a circular symmetric array). In various implementations, the minimumdifference in polar angle between any two angularly adjacent microphonesin a group (e.g., an outer or inner group excluding a centralmicrophone) of N microphones is no more than about 25, 30, 40, 45, 50,55, 60, or 65% of 360/N).

The combination of a relatively compact inner group of microphones 202j-202 p and a sparse, scattered outer group 202 a-202 i can also helpaccommodate additional componentry. For instance, in the illustratedembodiment, the radial distance of the outermost microphone 202 l in therelatively compact second group is 1.06 cm, or about 19% (1.06 cm/5.5cm) of the radius of the top board 216 a, and about 21% (1.06 cm/4.92cm) of the radial distance of the outermost microphone 202 h in thearray. In various implementations, the radial distance of the outermostmicrophone 202 l in the second group is no more than about 10, 15, 20,25, 30, or 35% of the radius of the board 216 a, or of the radialdistance of the outermost microphone 202 h in the array, therebymaintaining a compact geometry for the second group.

The wide variability in microphone radial distance between groupscreates additional space for mounting components. For example, theradial distance of the innermost microphone 202 m in the relativelycompact second group is 0.73 cm, or about 13% (0.73 cm/5.5 cm) of theradius of the top board 216 a, and about 15% (0.73 cm/4.92 cm) of theradial distance of the outermost microphone 202 h in the outer group. Invarious implementations, the radial distance of the innermost microphone202 l in the second group is no more than about 5, 10, 15, 20, 25, or30% of the radius of the board 216 a, or of the radial distance of theoutermost microphone 202 h in the first group, thereby maintaining acompact geometry for the second group.

Referring now to FIG. 3B, the bottom side of the top board 216 aaccommodates the microphones 202 a-202 p as well as additionalcomponents. The additional components in the illustrated embodimentinclude: hardware 214 including three mounting holes 304 andcorresponding periphery regions 306 configured to accept three PCBstandoffs 340 a-340 c of the bottom board 216 b (FIG. 3B); integratedcircuits 206 including i) a pulse density modulation to pulse codemodulation to time domain multiplexed (PDM to PCM to TDM) converter andchannel aggregator 308 a for format converting and aggregating audiosignals output by the outer group of microphones 202 a-202 i, ii) asecond PDM to PCM to TDM converter and channel aggregator 308 b forformat converting and aggregating signals output by the inner group ofmicrophones 202 j-202 p, iii) a first clock distribution integratedcircuit 312 a for sending clock signals to the first group ofmicrophones 202 a-202 i, and iv) a second clock distribution integratedcircuit 312 b for sending clock signals to the second group ofmicrophones 202 j-202 p; additional hardware 214 including a male boardto board connector 310 for electrically connecting the bottom board 216a and the top board 216 b (e.g., for routing PDM to PCM to TDM convertedmicrophone signals to the bottom board 216 b); and a number of discreteelectrical components including surface mount devices (SMDs) comprisinginductors 314, capacitors 316, and resistors 318; and a proximity sensor307, which can an optical sensor or other type of sensor be used todetect a user's hand over the microphone for temporary muting or othercontrol purposes.

FIG. 3C illustrates a top view of the bottom board 316 a. Mounted on thetop board 316 a of the illustrated embodiment are: hardware 214including a female board-to-board connector 330 for connecting with themale connector 310 of the top board 216 a, and the PCB standoffs 340a-340 c for spacing the two boards 216 a, 216 b when assembled;integrated circuits 206 including an SDRAM memory device 332, amicroprocessor 334, an Ethernet switch 336, and a power over Ethernet(POE) power controller 342; user interface components including six LEDs338 arranged around the periphery of the board 216 b to form a lightring; and discrete electrical components 204 including SMD inductors314, capacitors 316, and resistors 318.

Referring to FIG. 3D, following components are mounted to the bottom ofthe bottom board 216 of the illustrated embodiment: hardware 214including an Ethernet jack 350 for connecting to a network 130 andEthernet magnetics 352 for isolating the Ethernetconnection/componentry; discrete electrical components power supplytransformer 354, electrolytic capacitor 356, MOSFET transistors 358 a-b;and integrated circuits 206 including the voltage controlled oscillator360. During operation, the microprocessor 334 can package detected audiosignals to the Ethernet switch 336 a according to the Ethernet protocolfor delivery to the network 130 over the Ethernet jack 350.

In addition to providing improved flexibility for mounting components,asymmetric arrays can provide performance benefits. For example, havingvariable distances between the microphones in the array and reflectivesurfaces such as the outer case can prevent constructive interference,effectively spreading out and cancelling certain types of noise ascompared to symmetric designs.

The plots shown in FIG. 4 illustrate performance of the microphone array40 of FIGS. 3A-3D. As shown, the microphone system 140 of FIGS. 3A-3D,after beamforming and other appropriate processing by the processor 122,achieves good directionality in detecting 500 Hz sound at 0/360 degrees(upper left quadrant), 90 degrees (lower left quadrant), 180 degrees(lower right quadrant), and 270 degrees (upper right quadrant), whilemaintaining a flexible, asymmetric microphone placement geometry.Because the cross-over frequency between the first and second groups ofmicrophones 202 a-i, 202 j-p is about 1200 Hz, the plots primarily showperformance of the first group 202 a-202 i, which is used to detectsounds in a frequency range of about 20-1,200 Hz.

Single Board Embodiment Microphone System

While the embodiment of FIGS. 3A-3D is a dual-board configuration, insome cases it can be desirable to have a single board implementation,where the microphones and additional componentry in the microphonesystem 140 is accommodated on a single board. This can be advantageousfrom a visual design stand-point because it allows a slim, sleekaesthetic, or for functional reasons by allowing the microphone systemto fit into thinner, flatter form factors, such as for use in a ceilingtile or other space.

The design flexibility provided by the asymmetric microphonearrangements disclosed herein can be useful in enabling single-boardimplementations. FIG. 5 shows one example of a single board microphonesystem 140. Mounted on the microphone board 216 are microphones 202a-202 p arranged in a substantially similar arrangement to that of theembodiment of FIGS. 3A-3D, although different arrangements are possible.In addition, a large number of other components 308-360 are mounted onthe board 216. The components 308-360 can be the same as thelike-numbered components in FIGS. 3A-3D, although the system 140 of FIG.5 includes a second microprocessor 334 b.

As shown, the second microprocessor 334 b has a rather large footprint,illustrating how the asymmetric microphone arrangement can physicallyaccommodate components that a rigid symmetric array, such as an array ofconcentric rings, could not. In one embodiment, one or both of themicroprocessors 334 a, 334 b implement on-board fixed or adaptiveacoustic echo cancellation, on-board fixed or adaptive beamforming, orboth. Where echo cancellation and/or beamforming are performed on-boardthe microphone system 140 itself, one or both of the operations may beperformed in the frequency domain, and the microprocessors 334 a, 334 bare programmed to perform time to frequency conversion and frequency totime conversion to convert the signals into the frequency domain forfixed or adaptive echo cancelation and/or fixed or adaptive beamforming,and back to the time domain for further processing. In otherimplementations, one of echo cancelation or beamforming is performedon-board in the frequency domain and the other is performed on-board inthe time domain, and in yet further embodiments both are performedon-board in the time domain.

The combination of the compact second group of microphones 202 j-202 pand the relatively sparse first group 202 a-202 i allows for flexibleplacement of non-microphone components, including relatively largecomponents like the second processor 334 b and the Ethernet jack 350. Asshown, the radial distance of a number of the components (measured fromthe center of the board 216 to the center of the respective componentpackage) is greater than the radial distance of the microphone in thesecond group 202 j-202 p nearest to the component and less than theradial distance of the microphone in the first group 202 a-202 i nearestto the component (where “nearest” means the microphone having its centernearest to the center of the component package). As a few non-exhaustiveexamples: i) the radial distance of the microprocessor 334 a is greaterthan the radial distance of microphone 202 m and less than the radialdistance of the microphone 202 d; ii) the radial distance of the powersupply transformer 354 is greater than the radial distance of themicrophone 202 o and less than the radial distance of the microphone 202h; and iii) the radial distance of the voltage controlled oscillator 360is greater than the radial distance of the microphone 202 l and lessthan the radial distance of the microphone 202 c.

The relatively wide variability in radial distance between certainmicrophones in the outer group of microphones 202 a-202 i providesadditional flexibility. For example, the components 358 b and 354 arepositioned in the space between the two microphones 202 g, 202 h in theouter group that have the largest difference in radial distance.Moreover, the relatively wide variability in angular separation betweencertain microphones in the outer group of microphones 202 a-202 iprovides flexibility, evidenced by the placement of the relatively largeEthernet jack 350 between the microphones 202 f, 202 g having thelargest angular separation of any two angularly adjacent microphones inthe outer group 202 a-202 i.

While certain embodiments have been shown for the purposes ofillustration, other implementations are possible. For example, while themicrophone boards 216 of the illustrated embodiments are circular, othershapes (rectangle, square, triangle, ovals, etc.) are possible inimplementations. Moreover, while a particular arrangement of microphoneshas been shown, other arrangements are possible. For example,alternative implementations include arrangements in which themicrophones within one or both the groups are placed at differentlocations, arrangements where there are more than two groups ofmicrophones (e.g., three, four, five, or more groups), and/orarrangements where there are different numbers of microphones overall orwithin the groups. Moreover, there can be other numbers of microphonesin other embodiments, including 4, 8, 20, 24, 32, 36, 48 or moremicrophones. For instance, where acoustic echo cancellation is performedon the microphone system 140 itself, 20, 32, 48 or more microphones canbe included.

Microphone Array Construction

FIG. 6 is a flowchart showing an example of a method 600 of placingmicrophones asymmetrically in an array.

At step 602, any non-microphone components are placed on the substrate.For example, a user can use a computer-aided design (CAD) software toolto place one or more integrated circuits, discrete electricalcomponents, sensors, user interface components, physical hardware, orgenerally any of the additional components shown and/or describedherein, e.g., with respect to FIGS. 2, 3A-3D, and 5 .

At step 604, each microphone in a first group of microphones (e.g., themicrophones 202 a-202 i) are placed in an initial asymmetric arrangementin which each of the microphones has a unique polar angle and radiuswith respect to the center of a substrate. The placements may beselected by a user in a software design and/or simulation tool, or beautomatically selected by a computer (e.g., using an algorithm involvinga pseudorandom number generator). Whether manual or by computer, theplacements can in some embodiments be arbitrarily selected but withincertain constraints. For example, radius may be selected from a set ofavailable radiuses between a certain minimum radius and a certainmaximum radius. Moreover, the microphones cannot be placed where one ofthe additional non-microphone components were placed in step 602. Afurther constraint may require that the radiuses and/or the polar anglessatisfy some distribution profile within the range of possible values(e.g., at least some percentage of the microphones in the first groupbetween each of 0 and 90, 90 and 180, 180 and 270, and 270 and 360degrees).

At step 606, each microphone in a second group of microphones (e.g., themicrophones 202 j-202 n) are placed in an initial asymmetric arrangementin which each of the microphones has a unique polar angle and radiuswith respect to the center of a substrate. The placement can be made insubstantially the same fashion as for the first group, but withdifferent constraints (e.g., smaller minimum radius and smaller maximumradiuses to select from).

At step 608, microphone performance is simulated at the initialplacements. For example, the user may place the microphones using asoftware design tool, export the initial microphone placements to asoftware simulation tool, and simulate beamforming or other performancemetrics at the initial microphone placements using the simulation tool.

At step 610, one or more of the microphones in the first and/or secondgroup can be moved to an adjusted location. For example, a user mayreview performance a particular frequency range, and based on thereview, adjust the placement of one or more of the microphones in thedesign tool to a location on the substrate that should provide improvedperformance in that frequency range.

At step 612, microphone performance is again simulated and reviewed todetermine whether sufficient array performance has been achieved. Steps610 and 612 can be iterated to adjust placement of the microphones untilsufficient array performance is observed.

In alternative embodiments, placement of the non-microphone componentsat step 602 can be performed after placement of the microphones (aftersteps 604-612). Where step 602 is performed after placement of themicrophones, if there is not an adequate empty space on the substrate toplace an additional component (e.g., a relatively large IC) afterplacement of the microphones, steps 610-612 may need to be iterated tomove one or more of the microphones and free up space for the additionalcomponent.

Moreover, where step 602 is performed before placement of themicrophones, it could be the case that no placement of the microphonescan be found that provides sufficient array performance. In thiscircumstance, the initial placement of one more of the additionalcomponents can be adjusted before moving the microphones further to finda microphone placement that provides sufficient performance.

Once final microphone placements are found, the final placements arerecorded and/or output at step 614, e.g., by the software design tool.The microphone system can then be fabricated using the output, byphysically mounting the microphones on the PCB(s) according to theoutput obtained at step 614.

Terminology/Additional Embodiments

Conditional language used herein, such as, among others, “can,” “could,”“might,” “may,” “e.g.,” and the like, unless specifically statedotherwise, or otherwise understood within the context as used, isgenerally intended to convey that certain embodiments include, whileother embodiments do not include, certain features, elements and/orstates. Thus, such conditional language is not generally intended toimply that features, elements and/or states are in any way required forone or more embodiments or that one or more embodiments necessarilyinclude logic for deciding, with or without author input or prompting,whether these features, elements and/or states are included or are to beperformed in any particular embodiment.

Depending on the embodiment, certain acts, events, or functions of anyof the methods described herein can be performed in a differentsequence, can be added, merged, or left out altogether (e.g., not alldescribed acts or events are necessary for the practice of the method).Moreover, in certain embodiments, acts or events can be performedconcurrently, e.g., through multi-threaded processing, interruptprocessing, or multiple processors or processor cores, rather thansequentially.

The various illustrative logical blocks, modules, circuits, andalgorithm steps described in connection with the embodiments disclosedherein can be implemented as electronic hardware, computer software, orcombinations of both. To clearly illustrate this interchangeability ofhardware and software, various illustrative components, blocks, modules,circuits, and steps have been described above generally in terms oftheir functionality. Whether such functionality is implemented ashardware or software depends upon the particular application and designconstraints imposed on the overall system. The described functionalitycan be implemented in varying ways for each particular application, butsuch implementation decisions should not be interpreted as causing adeparture from the scope of the disclosure.

The various illustrative logical blocks, modules, and circuits describedin connection with the embodiments disclosed herein can be implementedor performed with a general purpose processor, a digital signalprocessor (DSP), an application specific integrated circuit (ASIC), afield programmable gate array (FPGA) or other programmable logic device,discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein.A general purpose processor can be a microprocessor, but in thealternative, the processor can be any conventional processor,controller, microcontroller, or state machine. A processor can also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

The blocks of the methods and algorithms described in connection withthe embodiments disclosed herein can be embodied directly in hardware,in a software module executed by a processor, or in a combination of thetwo. A software module can reside in RAM memory, flash memory, ROMmemory, EPROM memory, EEPROM memory, registers, a hard disk, a removabledisk, a CD-ROM, or any other form of computer-readable storage mediumknown in the art. An exemplary storage medium is coupled to a processorsuch that the processor can read information from, and write informationto, the storage medium. In the alternative, the storage medium can beintegral to the processor. The processor and the storage medium canreside in an ASIC. The ASIC can reside in a user terminal. In thealternative, the processor and the storage medium can reside as discretecomponents in a user terminal.

While the above detailed description has shown, described, and pointedout novel features as applied to various embodiments, it will beunderstood that various omissions, substitutions, and changes in theform and details of the devices or algorithms illustrated can be madewithout departing from the spirit of the disclosure. As will berecognized, certain embodiments of the disclosures described herein canbe embodied within a form that does not provide all of the features andbenefits set forth herein, as some features can be used or practicedseparately from others. The scope of certain disclosures disclosedherein is indicated by the appended claims rather than by the foregoingdescription. All changes which come within the meaning and range ofequivalency of the claims are to be embraced within their scope.

What is claimed is:
 1. An acoustic microphone array system, comprising:a substrate; and an array of acoustic microphones including a firstgroup of acoustic microphones placed on the substrate in an asymmetricpattern and a second group of microphones, wherein the radial distanceof each microphone in the first group of microphones is larger than theradial distance of each microphone in the second group of microphones.2. The system of claim 1 wherein the second group of microphones isplaced on the substrate in an asymmetric pattern.
 3. The system of claim1 wherein a radial distance of an innermost microphone in the secondgroup of microphones is no more than about 25% of a radial distance ofan outermost microphone in the first group of microphones.
 4. The systemof claim 3 further comprising one or more packaged integrated circuitsplaced on the substrate at a radial distance greater than the radialdistance of the innermost microphone in the second group and less thanthe radial distance of the outermost microphone in the first group. 5.The system of claim 1 wherein the radial distance of an innermostmicrophone in the first group of microphones is no more than 50% of theradial distance of an outermost microphone in the first group ofmicrophones.
 6. The system of claim 5 further comprising one or morepackaged integrated circuits placed on the substrate at a radialdistance between the radial distance of the innermost microphone in thefirst group of microphones and the radial distance of the outermostmicrophone in the first group of microphones.
 7. The system of claim 1wherein the first group of microphones includes N microphones, and themaximum difference in polar angle between any two angularly adjacentmicrophones of the first group of microphones is at least 130% of 360/N.8. The system of claim 7 further comprising a packaged integratedcircuit placed between angularly adjacent microphones in the first groupof microphones.
 9. The system of claim 1 further comprising a group ofpackaged integrated circuits mounted on the substrate together with thefirst and second groups of microphones, the group of packaged integratedcircuits comprising one or more networking devices and one or moremicroprocessors.
 10. The system of claim 1 further comprising aprocessor placed on the substrate and configured to perform one or bothof acoustic echo cancelation and beamforming on signals output by thefirst and second groups of microphones.
 11. The system of claim 1further comprising a processor configured to combine signals output bythe first group of acoustic microphones to generate output sound withina first frequency range and to combine signals output by the secondgroup of acoustic microphones to generate output sound within a secondfrequency range.
 12. The system of claim 11 wherein the first and secondfrequency cover a combined frequency that at least includes frequenciesfrom 1,000 Hz to 14,000 Hz.
 13. The system of claim 12 wherein a maximumfrequency in the first frequency range is substantially less than 14,000Hz, and a minimum frequency of the second frequency range issubstantially more than 1,000 Hz.
 14. The system of claim 11 wherein theprocessor is remote from the first and second groups of microphones, andin communication with the first and second groups of microphones via anetwork.
 15. The system of claim 1 wherein the substrate is circular.16. An audio system, comprising: a substrate; an array of acousticmicrophones including a first group of acoustic microphones arranged onthe substrate in an asymmetric pattern and a second group of acousticmicrophones arranged on the substrate in an asymmetric pattern, whereinthe radial distance of an innermost microphone of the first group ofmicrophones from a center of the substrate is greater than a radialdistance of an outermost microphone of the second group of microphonesand no more than about 40% of the radial distance of an outermostmicrophone of the first group of microphones, and the radial distance ofthe outermost microphone in the second group of microphones is no morethan about 25% of the radial distance of the outermost microphone in thefirst group of microphones; and a processor configured to combinesignals output by the first group of acoustic microphones to generateoutput sound within a first frequency range and to combine signalsoutput by the second group of acoustic microphones to generate outputsound within a second frequency range.
 17. The system of claim 16wherein the processor is remote from the first and second groups ofmicrophones, and in communication with the first and second groups ofmicrophones via a network.
 18. A method of generating a microphonelayout for an array microphone, comprising: placing each microphone infirst and second groups of microphones in an arbitrary initial positionon the substrate, wherein subsequent to said placing each microphone,the microphones are arranged at an initial set of microphone positions;with a software simulator, determining array performance with themicrophones at the initial set of microphone positions; subsequent tosaid determining array performance, adjusting placement of one or moremicrophones in one or both of the first group of microphones and thesecond group of microphones such that the microphones are arranged at anadjusted set of microphone positions; with the software simulator,determining adjusted array performance at the adjusted set of microphonepositions; repeating said adjusting placement and determining adjustedarray performance said adjusted array performance indicates sufficientperformance at a set of final microphone positions in which the firstgroup of microphones is arranged in a first asymmetric pattern and thesecond group of microphones is arranged in a second asymmetric pattern;and placing a plurality of non-microphone components on a substrate. 19.The method of claim 18 wherein at the set of final microphone positions,each microphone in the first group is located at a longer radialdistance from the center of the substrate than each microphone in thesecond group.
 20. The method of claim 18 wherein said placing theplurality of non-microphone components is performed prior to saidplacing each microphone in the first and second groups of microphones inan initial position on the substrate.